9,10-[3H]Palmitic, 1-[14C]arachidonic and 1-[14C]docosahexaenoic acids have been shown to be appropriate fatty acids for the study of phospholipid metabolism. Ex-vivo experiments in rats have clearly demonstrated that each of these fatty acids are rapidly and selectively incorporated into brain phospholipids. For example, the rate of incorporation of arachidonic acid into brain is related to its synthesis and/or turnover into the sn-2 positions of phosphatidyl inositol and choline while palmitic acid is related to its turnover into the sn-1 positions of phosphatidyl choline1-3. In an effort to extend this work to the in vivo evaluation of regional brain phospholipid metabolism using PET, we have developed a remote radiosynthesis for 1-[11C]arachidonic acid and 1-[11C]docosahexaenoic acid4. A facile retro-synthesis involving the radical chain decarboxylation of the N-hydroxypyridine-2-thione esters of both arachidonic and docosahexaenoic acid was developed to synthesize (all Z)-1-bromononadeca- 4,7,10,13-tetraene, and (all Z)-1-bromoheneicosa-3,6,9,12,15,18-hexaene in 60% overall yield. The corresponding polyhomoallylic magnesium bromides were carbonated with [11C]C02 to afford the 1- [11C]polyhomoallylic labeled fatty acids in good yield in less than 35 minutes. The final radiochemical purities were found to be in excess of 95% by radio-HPLC. A remote radiosynthetic apparatus has been fabricated and has been utilized to routinely prepare in excess of 60 mCi of each C-11 palmitic, arachidonic, and docosahexaeneoic acids. Preparations of these radiotracers have been successfully used in rhesus monkey to measure whole body distribution and regional rates of brain uptake by PET.